RTMP
The protocol your encoder — OBS, vMix, Zoom or a hardware box — uses to send a live signal to the platform. Today it is for ingest, not playback.
RTMP (Real-Time Messaging Protocol) carries the live signal from the encoder to the streaming platform. Viewers no longer watch RTMP: the platform transcodes the stream and delivers it over HLS. Its alternatives are RTMPS, which is encrypted, and SRT, which copes better with unstable networks.
What is RTMP?
RTMP is a protocol Macromedia, later Adobe, created to move audio and video in real time between a server and the Flash player. Flash disappeared from browsers, but RTMP took another job: carrying a live signal from where it is produced to the platform that processes it.
It runs over TCP, usually on port 1935, and keeps a connection open while the encoder streams continuously. Its big strength is compatibility: practically every streaming app, mobile app and hardware encoder speaks RTMP.
Where RTMP sits in a live stream
Camera, microphone, screen or a production switcher.
OBS, vMix, Larix, Zoom or a hardware encoder compresses the signal, usually in H.264H.264 (AVC)The most compatible video codec: practically every browser, phone and smart TV plays it. The safe format to upload and deliver.Open definition →, at the bitrate you choose.
The signal travels to the platform using the server URL and the stream key. This is the only leg where RTMP is used.
The platform transcodes the signal into several qualities and delivers them through a CDNCDN (Content Delivery Network)A global network of edge servers that caches video close to viewers, cutting latency and absorbing traffic spikes.Open definition → over HLSHLS (HTTP Live Streaming)Apple’s adaptive streaming protocol. Uses .m3u8 manifests and segmented delivery; supported on every browser, device and smart TV.Open definition →, which every browser and phone plays.
Server URL and stream key
| Setting | What it is | Format example |
|---|---|---|
| Server URL | The address of the ingest server | rtmp://server/live |
| Stream key | The secret identifier of your event | A long, unique string |
Anyone with the key can stream into your event: treat it like a password and regenerate it if it was shown on screen.
RTMP vs RTMPS vs SRT
| RTMP | RTMPS | SRT | |
|---|---|---|---|
| Transport | TCP | TCP with TLS encryption | UDP with packet recovery |
| Encryption | No | Yes | Yes |
| On unstable networks | Struggles: drops add up | Same as RTMP | Handles packet loss better |
| Compatibility | Universal | Very wide | Wide and growing |
Rule of thumb: RTMPS for a stable office or studio connection; SRT for mobile, outdoor events or long distances.
Further reading
- Kinescope: connecting the stream — RTMP servers and supported encoders.
- Live streaming — the whole live pipeline.
